1. Field of the Invention
The present invention relates generally to a Multimedia Broadcast/Multicast Service (MBMS) in a mobile communication system, and more particularly to a method for minimizing false alarms based on a notification of an existence or absence of control information for the MBMS to a User Equipment (UE).
2. Description of the Related Art
Currently, with the development of communication technology, a conventional mobile communication system providing a voice service is being developed into a packet service communication system capable of transmitting mass storage data, such as packet data and circuit data, and a multimedia broadcast/communication system capable of transmitting a multimedia service. Accordingly, in order to support the multimedia broadcast/communication system, an MBMS for providing a service to a plurality of UEs from at least one multimedia data source has been discussed.
Generally, an MBMS transmits the same multimedia data to a plurality of receivers through a radio network. Herein, the plurality of receivers share one radio channel, such that radio transmission resources can be saved. Because an MBMS transmits multimedia data such as image data, voice data, still image data and text data in real-time, and simultaneously provides voice data and image data according to the types of the multimedia data, the MBMS requires a large quantity of transmission resources.
In an MBMS, because the same data must be transmitted to a plurality of cells including users, a Point-to-Point (PtP) or a Point-to-Multi-Point (PtM) connection is used according to the number of users located in each cell. That is, the PtP provides an MBMS requested by each UE through a dedicated channel allocated to each UE, while the PtM provides a corresponding service to UEs requesting the same MBMS through a common channel allocated to each MBMS.
In the description of the present invention, a 3G asynchronous mobile communication network proposed by the 3rd Generation Project Partnership (GPP) is described as one example of a mobile communication network. However, the present invention can be applied to another mobile communication network using an MBMS.
FIG. 1 is a diagram illustrating one example in which a conventional 3G asynchronous mobile communication network proposed by the 3rd Generation Partnership Project (GPP), provides an MBMS. More specifically, FIG. 1 illustrates nodes joining the MBMS provided by the 3GPP mobile communication network.
Referring to FIG. 1, a Core Network (CN) 100 supplies an MBMS, transmits the MBMS to a UMTS Radio Access Network (UTRAN) 110, and authenticates UEs 120 to 122. The UTRAN 110 connects the CN 100 to the UEs 120 to 122, and allocates and manages wired/wireless resources for transmission of the MBMS. Further, the UTRAN 110 includes a Radio Network Controller (RNC) 111 and a node B 112. The RNC 111 may control a plurality of node Bs in addition to the node B 112. Herein, each of the node Bs including the node B 112 includes a plurality of cells. Accordingly, the cells can be distinguished from another according to frequencies or locations of each cell.
Each of the UEs 120 to 122 can receive the MBMS. Additionally, a plurality of UEs may exist in each cell.
In the MBMS, a basic service unit is a cell and the service is provided through a PtP scheme or a PtM scheme in consideration of radio environments of the cell and the number of UEs to receive the MBMS.
In order to provide the MBMS, it is necessary to report a start of the MBMS or a start of a session (basic unit of MBMS transmission in a CN) of a random MBMS, and count the number of UEs for determining one of the PtP scheme and the PtM scheme used for providing the MBMS.
When the MBMS is provided through the PtM scheme according to the counting process, it is necessary to report channel information for receiving the MBMS through the PtM scheme and transmit a plurality of control information, such as notification for change of the transmission scheme (PtP and PtM), while the MBMS is being provided. Further, it is necessary to provide a method for informing UEs if the control information is transmitted.
FIG. 2 is a diagram illustrating a Paging Channel (PCH) and a paging method for informing a UE that a voice service, a packet service, or control information is transmitted in a conventional 3GPP communication network. Referring to FIG. 2, a Paging Indicator Channel (PICH) 220 has a length of 10 ms. The PICH 220 is a channel transmitted after being band-spread with spreading factor 256 and may transmit 300 bits for each 10 ms. Herein, 12 bits 223 of the 300 bits are allocated as a currently unused portion, and represent bits reserved for expansion of a mobile communication system in the future.
Accordingly, the PICH 220 may transmit 288 bits for each 10 ms. That is, the PICH 220 may transmit Paging Indicators 221 (PIs) ranging from a minimum of 18 to a maximum of 144 bits for each 10 ms. Herein, each PI includes two bits at minimum and 16 bits at maximum. The number of the PIs that can be transmitted for each 10 ms can be determined using the number of UEs requesting paging.
When the PI 221 has a positive value (+1), the UE receives a PCH transmitting paging information for the UE and finally confirms paging for the UE. However, when the PI 221 has a negative value (−1), the UE waits to receive the next PICH, and then confirms the value of the PI. The PCH transmits detailed paging information, which includes an identifier of a UE and cause values for reporting the paging cause for the UE, to a UE having confirmed the PI. Accordingly, the UE may finally confirm if the UE has been paged only after receiving the detailed paging information. That is, the UE may confirm that the UE has been paged only after checking the PI having a positive value and receiving the PCH. Herein, the step of receiving the PI having the positive value will be referred to as “primary paging” and the step of confirming final paging after receiving the PCH will be referred to as “secondary paging”.
Generally, a 3GPP mobile communication network provides a method of confirming if paging information exists in a specific location according to each UE, in order to reduce battery consumption of the UEs. This method prevents the UE from continuously receiving a PICH for continuously confirming if the UE has been paged even when the UE does not actually use a voice service or a data service. That is, the method prevents the battery consumption of the UE from increasing because of continuous reception of the PICH.
Accordingly, a UE receives the PICH only in a CN Discontinuous Reception (DRX) cycle or a UTRAN DRX cycle 200 and confirms if paging information exists. That is, the CN DRX cycle or the UTRAN DRX cycle 200 is a parameter used for saving the power of the UE. The CN DRX cycle is a value determined by a CN and the UTRAN DRX cycle is a value determined by a UTRAN for use. The CN DRX cycle or the UTRAN DRX cycle 200 is transmitted to UEs in a cell through a Broadcast Channel (BCH) transmitting system information.
When a UE is in a Radio Resource Control (RRC) connection state with a UTRAN, the UE confirms that primary paging information for the UE exists by using the UTRAN DRX cycle. Further, when the UE is in an idle mode, the UE confirms that the primary paging information for the UE exists by using the CN DRX cycle.
The CN DRX cycle or the UTRAN DRX cycle 200, as described above, reduces battery consumption of the UE, and also prevents UEs from confusing primary paging for other UEs as primary paging for the UEs themselves because of the dispersion of paging signals for the UEs in a mobile communication network, thereby reducing unnecessary operation of receivers of the UEs.
For example, when 18 PIs are transmitted through one PICH and the CN DRX cycle is 1.28 seconds, the number of PIs actually used for paging a UE is 2304 (18×128). When it is assumed that the number of UEs waiting for paging in a mobile communication network is 10,000 and primary paging for a UE is distinguished by only a PI of a PICH, one PI may report existence of primary paging for about 556 UEs. Even when primary paging for only one UE exists, the remaining 555 UEs also receive the PCH and finally confirm secondary paging. When the DRX cycle is used, about 5 UEs correspond to one PI. Further, when it is reported that primary paging for one UE exists, the number of UEs unnecessarily receiving a PCH for secondary paging is reduced to four.
FIG. 3 is a diagram illustrating a conventional example for reporting an existence of control information for an MBMS in a mobile communication system providing the MBMS.
A method for reporting existence of control information according to offer of an MBMS in a 3GPP is similar to an existing paging scheme for reporting existence of general control information according to a voice service or a packet service. That is, a final paging is confirmed through reception of a paging message after a PI is received.
Referring to FIG. 3, in relation to the above-description, the 3GPP defines an MBMS Specific Paging Indicator Channel (MICH) 320 in order to report paging of the control information for the MBMS. Notification Indicators (NIs) 321 and 322 are transmitted through the MICH for reporting the existence of paging for the MBMS. The notification represents notifying UEs having joined a predetermined MBMS of a start of the MBMS or a session start of the MBMS, and existence of control information relating to the MBMS. Further, a notification message is transmitted through an MBMS Common Control Channel (MCCH) defined for transmitting MBMS control information.
Herein, the reception of an NI having a positive value by a UE supporting an MBMS will be referred to as a “primary notification”, and the reception of a notification message transmitted through an MCCH or other control information will be referred to as a “secondary notification”.
Additionally, the 3GPP has not defined a separate DRX cycle for an MBMS in order to reduce battery consumption of a UE receiving the MBMS. This prevents a receiver of the UE from unnecessarily operating twice according to two paging cycles, i.e., one DRX cycle for a primary paging with respect to a service (a general packet service or circuit service), except for the MBMS, and the other DRX cycle for a primary notification for the MBMS.
As described above, the DRX cycle for the MBMS has not been defined, such that the battery of the UE can be prevented from being consumed. However, as described in FIG. 2, it is problematic in that a method of increasing the number of PIs by using the DRX cycle is not used. Further, there is a problem in that the number of UEs unnecessarily receiving an MCCH for a secondary notification increases according to an increase in the number of MBMSs corresponding to an NI for a primary notification.
For example, when it is assumed that 1000 MBMSs exist in a 3GPP mobile communication system and 18 NIs exist in an MICH, 56 services corresponds to one NI for a primary notification. Herein, when it is considered that each MBMS is provided to a plurality of UEs and a primary notification is performed for a plurality of MBMSs, simply by using NIs of an MICH, without an MBMS specific DRX cycle, there is a problem in that UEs must unnecessarily confirm MCCHs for a secondary notification for the MBMS.